With the recent progression of the so-called information-oriented society, electronic apparatuses typified by personal computers and PDAs (personal digital assistants) have come to be widely used. The spread of such electronic apparatuses has produced a demand for portable apparatuses that can be used both in offices and outdoors, and such apparatuses are required to be reduced in size and weight. As a means of achieving this object, liquid crystal display devices are widely used. Liquid crystal display devices are an indispensable technology not only for the reduction in size and weight but also for the reduction in the power consumption of battery driven portable electronic apparatuses.
Liquid crystal display devices are broadly classified into a reflective type and a transmissive type. The reflective type has a structure in which the light incident from the front surface of the liquid crystal panel is reflected at the back surface of the liquid crystal panel and the image is made to be visually seen by means of the reflected light. The transmissive type has a structure in which the image is made to be visually seen by means of the transmitted light from a light source (backlight) provided on the back surface of the liquid crystal panel. Since the reflective type in which the amount of reflected light varies depending on the environmental condition is inferior in viewability, transmissive type color liquid crystal display devices using color filters are generally used as display devices, particularly, for personal computers and the like that perform multi-color or full-color display.
At present, active driven type liquid crystal display devices using switching elements such as TFTs (thin film transistors) are widely used as color liquid crystal display devices. In the TFT driven liquid crystal display devices, although the display quality is high, since the light transmittance of the liquid crystal panel is only approximately several percent under present circumstances, a high-brightness backlight is necessary to obtain high screen brightness. For this reason, the power consumption of the backlight is increased. In addition, since color filters are used for color display, one pixel is necessarily formed of three subpixels, so that high resolution is difficult to achieve and the display color purity is insufficient.
To solve this problem, the present inventor et al. have developed field sequential type liquid crystal display devices (see, for example, Non-Patent Documents 1, 2 and 3). In the field sequential type liquid display devices, compared with the color filter type liquid crystal display devices, since no subpixel is required, higher-resolution display can be easily realized, and since the luminous colors of the light source can be used for display as they are without the use of color filters, the display color purity is excellent. Further, since light use efficiency is high, power consumption is low. However, to realize the field sequential type liquid crystal display devices, it is essential that the liquid crystal have a fast responsivity (equal to or less than 2 ms).
Accordingly, to achieve a fast responsivity in the field sequential type liquid crystal display devices having excellent advantages as mentioned above or the color filter type liquid crystal display devices, the present inventor et al. have researched and developed the driving of a liquid crystal such as a ferroelectric liquid crystal having spontaneous polarization from which a fast responsivity of 100 to 1000 times that of conventional devices can be expected, by switching elements such as TFTs (see, for example, Patent Document 1). In the ferroelectric liquid crystal, the direction of the major axis of the liquid crystal molecules tilts by voltage application. A liquid crystal panel holding the ferroelectric liquid crystal is sandwiched between two polarizing plates where the polarization axes of which are orthogonal to each other, and the intensity of transmitted light is changed by using the birefringence caused by the change of the optical axis involved in the change of the major axis direction of the liquid crystal molecules.
[Patent Document 1] Japanese Patent Application Laid-Open No. H11-119189
[Non-Patent Document 1] T. Yoshihara et al., ILCC 98, P1-074, issued in 1998
[Non-Patent Document 2] T. Yoshihara et al., AM-LCD' 99 Digest of Technical Papers, p. 185, issued in 1999
[Non-Patent Document 3] T. Yoshihara et al., SID'00 Digest of Technical Papers, p. 1176, issued in 2000